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I fitted a second (nearly identical) wheelset, and now my derailleur indexing is not working. Shifting into the last sprocket is not working, and there are a lot of gears over the range not working properly.

I am suspecting that a spacer is the culprit.

Parts

Original Hub: FH-RS470 (Cup&Cone) with a CS-M7000 (11-40T)

New Hub: WH-RX570 (Cup&Cone) with a CS-M8000 (11-40T)

Discs of both wheels fit perfectly without adjustment of the brakes. Consequently, I consider the general layout of the hubs as fine.

I also specifically bought the parts to be as identical as possible for easy swapping.

Potentially faulty Installation

However the new wheelset is considered Shimano Road, and the CS-M8000 is a MTB-cassette. It comes with a spacer (1.85mm) for Shimano Road freewheels.

Consequently, I installed the spacer first, and then the rest of the cassette.

Now, the indexing on the new set is not correct. E.g. I am unable to shift into the smallest 11T sprocket. Without the spacer left of the cassette, the cassette would sit slightly more to the left, so that "reaching" the smallest sprocket is possible.

Question

What did I do wrong during install?

  1. Spacer shouldn't even be there.
  2. Spacer should be installed last, so that the cassette sits slightly more to the left.

What would you recommend as next steps?

1 Answer 1

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What you did was correct: road free-hubs are larger than MTB ones, and fitting a MTB cassette requires to insert a spacer before inserting the cassette.

In your case, you focused on the new wheelset, but did you check if your original wheelset has been installed correctly? The CS-M7000 and CS-M8000 are both MTB cassettes, and both free-hubs are road and so you should have a spacer on the original wheelset too.

But if the spacer was "forgotten" in your original wheelset, indexing would be done on a shifted cassette, which would work perfectly fine, but will not transpose nicely with your new wheelset, that is in fact correct.

So my recommendation would be check whether a spacer is installed on the original wheelset, and if not, to install one. If there's one, check that it is a 1.85mm one.

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  • +1, the most common cause of what's going on here is the spacer(s) on the original FHB were close enough to do the job but not the correct Shimano-sanctioned 1.85mm type. Jul 4, 2022 at 3:22
  • I've had 2k trouble-free km with the original factory installed (orbea) wheelset. Thank you for your suggestions, I will first try the new wheelset without the spacer, and if that does not work buy an additional spacer for the original wheelset for both sets to be identical. I will report back once I have results
    – a1o
    Jul 4, 2022 at 20:06
  • The guys from the Orbea factory did indeed not use a spacer, you were right. Both wheel sets function flawlessly now without any adjustment
    – a1o
    Aug 5, 2022 at 10:30

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